Use of block copolymers as dispersants for aqueous suspensions of solids

ABSTRACT

The use of block copolymers which were prepared by polymerization of a poly(alkylene oxide) compound (A) with at least one ethylenically unsaturated monomer compound (B), as dispersants for aqueous suspensions of solids, in particular based on hydraulic binders, such as, for example, cement, lime, gypsum or anhydrite, is described. Surprisingly, these block copolymers have a substantially better water-reducing power at the same dose in comparison with conventional superplasticizers based on comb polymers. Moreover, the slump loss can also be reduced in comparison with conventional superplasticizers by modification of the adhesive block.

The present invention relates to the use of block copolymers which wereprepared by polymerization of a poly(alkylene) oxide compound (A) withan ethylenically unsaturated monomer compound (B), as dispersants and/orsuperplasticizers for aqueous suspensions of solids, in particular basedon hydraulic binders, such as, for example, cement, lime, gypsum oranhydrite.

In aqueous suspensions of pulverulent inorganic or organic substances,such as hydraulic binders (cement, lime, gypsum or anhydrite), crushedrock, silicate powder, chalk, clays, porcelain slip, talc, pigments,carbon black or plastics powders, additives are often introduced in theform of dispersants in order to improve their processability, i.e.kneadability, flowability, sprayability, brushability or pumpability. Byadsorption onto the surfaces of the particles, these additives arecapable of breaking up agglomerates and dispersing the particles formed.Particularly in the case of highly concentrated dispersions, this leadsto a substantial improvement in the processability.

In the preparation of mixtures of building materials which containhydraulic binders, such as cement, lime gypsum or anhydrite, this effectcan be particularly advantageously utilized since otherwisesubstantially more water would be required for achieving a processableconsistency than would be required for the subsequent hydration orhardening process. The water which gradually evaporates after thehardening leaves behind cavities which have a significant adverse effecton the mechanical properties and stabilities of the structures.

In order to reduce the excess proportion of water after hydration and/orto optimize the processability at a predetermined water/binder ratio,additives which are generally referred to as superplasticizers are used.

The superplasticizers still most frequently used are polycondensatesbased on naphthalene- or alkylnaphthalanesulfonic acids (cf. EP-A 214412) and melamine/formaldehyde resins which contain sulfo groups (GermanPatent 16 71 017).

However, these superplasticizers have the disadvantage that their goodplasticizing effect—in particular in concrete construction—persists onlyfor a relatively short time span even at relatively high doses. Thisdecrease in the flowability of concrete mixes is also referred to asslump loss. It leads to problems particularly when relatively long timespans occur between the production of the concrete and the incorporationthereof, as often occurs due to long transport or conveying distances.

Furthermore, the liberation of the toxic formaldehyde contained as aresult of the production can lead to adverse work hygiene effects if theapplication takes place indoors (production of prefabricated concretepaths or drying of gypsum plasterboard) or in mining or tunnelconstruction.

In order to overcome these disadvantages, formaldehyde-freesuperplasticizers based on maleic monoesters and styrene were alsodeveloped (cf. EP-A 306 449). Although a high dispersing power over asufficient period (low slump loss) can be ensured with these additives,the positive properties are rapidly lost on storage of the aqueousformulations of these superplasticizers. The short shelf-life of thesesuperplasticizer solutions is due to the easy hydrolyzability of themaleic monoesters.

In order to overcome this problem, various superplasticizers stable tohydrolysis were developed. All these superplasticizers are copolymers ofethylenically unsaturated carboxylic acids (such as, for example,acrylic acid, methacrylic acid or maleic acid or salts thereof) andpoly(alkylene oxides) having a polymerizable terminal group (such as,for example, methacrylates, allyl ethers or vinyl ethers). Theincorporation of these long-chain monomers into a polymer chain leads topolymers having a comb-like structure (cf. U.S. Pat. No. 5,707,445, EP 1110 981 A2, EP 1 142 847 A2).

These comb polymers are distinguished not only by a long shelf-life butalso by substantially improved efficiency in comparison withsuperplasticizers based on lignin, naphthalene or melamine condensate.

According to a further accepted theory, the efficiency of thesuperplasticizers is based on two different effects. Firstly, thenegatively charged acid groups of the superplasticizers are adsorbed onthe cement particle surface positively charged by means of calcium ions.The electrostatic double layer (zeta potential) thus formed leads to anelectrostatic repulsion between the particles. The repulsive forcescaused by the zeta potentials, however, have only short ranges (cf. H.Uchikawa, Cement and Concrete Research 27 [1 ] 37-50 (1997)).

Furthermore, however, the physical presence of the adsorbedsuperplasticizer also prevents the surfaces of the cement particles frombeing able to come into contact with one another. This steric repulsiveeffect is dramatically enhanced by the unadsorbed side chains of theabovementioned comb polymers (cf. K. Yoshioka, J. Am. Ceram. Soc. 80[10] 2667-71 (1997)). It is obvious that the sterically caused repulsiveeffect can be influenced both by the length of the side chains and bythe number of side chains per main chain. On the other hand, a sidechain density or length which is too high can hinder the adsorption onthe cement particle surface. In order to determine the degree ofadsorption of a superplasticizer on cement particles, the content oforganic material in the superplasticizer is determined after addition ofsaid superplasticizer to the mixing water (TOC analysis). After thecement has been stirred in and after a short waiting time, the cementpaste is pressed and the collected pore water is again analyzed by meansof TOC. The decrease in the TOC value now corresponds to the proportionof the adsorbed superplasticizer. On the basis of such measurements, itwas possible to show that large parts of the superplasticizer are notadsorbed. This is not surprising since the side chains are present insolution not in the extended form but presumably rather in coiled form.Thus, carboxylate groups in the immediate neighborhood of the side chainare spatially shielded from the cement particle and cannot contribute tothe adsorption. Moreover, the preparation of the superplasticizers viafree radical copolymerization of a plurality of different monomers leadsto relatively nonuniform products with regard to molecular weight andside chain density. It is therefore not surprising that a part of thesesuperplasticizers are not adsorbed on the cement particle surface butremain dissolved in the pore water. When the main chain is too short orthe side chain density too high, for example, the number of carboxylgroups accessible for the cement particle surface cannot be sufficient.Main chains which are too long and have a low side chain density can, onthe other hand, bridge cement particles and thus promote flocculation.Presumably, these unadsorbed fractions make no contribution to thewater-reducing power of the superplasticizer.

As already mentioned, the polymeric superplasticizers forcement-containing systems according to the prior art to date arecopolymers having a comb-like structure which are prepared via freeradical polymerization. All these products are distinguished by highnonuniformity with regard to the number of side chains per polymermolecule and with regard to the molecular weight. However, it is knownthat an optimum molecular weight and an optimum number of side chainsper polymer molecule exist for each application and each cement type.All components of a product which deviate from this optimum thereforereduce the efficiency of the product or necessitate larger doses.

It was therefore the object of the present invention to provide polymercompounds which do not have said disadvantages of the prior art but,owing to an increased product uniformity and a low proportion of lesseffective components, have a substantially improved effect asdispersants or superplasticizers for aqueous suspensions of solids.

This object was achieved by the use of block copolymers which wereprepared by polymerization of a poly (alkylene) oxide compound (A) withat least one ethylenically unsaturated monomer compound (B).

Surprisingly, block copolymers which preferably consist of only apoly(oxyalkylene) chain with a terminally grafted-on adhesive block havea substantially better water-reducing power at the same dose thanconventional superplasticizers based on comb polymers. By modificationof the adhesive block, it is also possible to reduce the slump loss incomparison with conventional superplasticizers, which was likewise notforeseeable.

The block copolymers used according to the invention consist of at leasttwo polymeric building blocks of different chemical composition whichwere prepared by polymerization of a poly(alkylene) oxide compound (A)with an ethylenically unsaturated monomer compound (B).

Block copolymers having the structure A′-B′, i.e. block copolymers whichhave exactly one block A′ formed from a poly(alkylene oxide) compound(A) and exactly one block B′ formed from one or more differentethylenically unsaturated monomer compound (B) are particularlypreferred.

The preparation of the block copolymers is preferably effected bygrafting onto that end of the poly(alkylene oxide) compound (A) which issubstituted by the building block Z, by polymerizing on the monomercompound (B) either by free radical, anionic or cationic polymerization.The building block Z performs the function of polymerization initiator.Free radical polymerization is preferred here, in particular techniquesof controlled or living free radical polymerization, since thesetolerate a large number of different functional groups and solvents. Themethod of “atom transfer radical polymerization”, abbreviated below toATRP, is to be regarded as being very particularly preferred.

The poly(alkylene oxide) compound (A) used according to the inventioncorresponds here to the general formula I

in which R¹ has the following meaning: a hydrogen atom, an aliphatichydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic radicalhaving 5 to 12 C atoms or an aryl radical having 6 to 14 C atoms whichmay optionally also be substituted. The following is applicable for theindices: m=2 to 4 and n=1 to 25, where m can preferably assume thevalues 2 or 3 and n preferably values of from 5 to 250 and even morepreferably values of from 20 to 135.

Cyclopentyl or cyclohexyl radicals are to be regarded as preferredcycloalkyl radicals, and phenyl or naphthyl radicals which in particularmay also be substituted by hydroxyl, carboxyl or sulfo groups are to beregarded as preferred aryl radicals.

In the context of the present invention, the building block Z in formulaI may have the following meanings: Z may be derived from2-haloalkylcarboxylic acid derivatives of the general formula III:

Here, X may be Cl, Br or I, m′ may be 1 to 4 and n′ may be 0, 1 or 2,m′=1 and n′=0 or 1 being preferred. Y may be O or NR² and R² may be H,an alkyl radical having 1 to 12 C atoms or an aryl radical having 6 to14 C atoms and

-   -   R¹, m, and n having the abovementioned meaning. R² is preferably        H, CH₃ or C₂H₅.

Z may furthermore be derived from the arylsulfonyl halide derivativesaccording to formula IV:

Here, X is once again Cl or Br, preferably Cl. R³ may be an aromaticradical having 6 to 14 C atoms, preferably a phenyl or naphthyl radical,which may also be substituted by halo, hydroxyl, C₁-C₁₂-alkoxy,C₁-C₁₂-dialkylamino or carboxyl groups.

In the context of the present invention, the building block Z mayfinally also be chain-transferring groups in the form of thiols,secondary amines, phosphines or derivatives of phosphorous acidaccording to the general formula V

-   -   in which R⁴ is H, a C₁-C₁₂-alkyl radical, a C₅-C₈-cycloalkyl        radical, a C₈-C₁₄-aryl radical optionally substituted by        hydroxyl, carboxyl or sulfo groups, or

and R⁵ is C₁-C₁₂-alkyl, C₆-C₁₄— aryl or

and R¹, R², m and n have the abovementioned meaning. Preferred alkylradicals are methyl or ethyl, preferred cycloalkyl radicals arecyclopentyl or cyclohexyl and preferred aryl radicals are phenyl ornaphthyl.

The preparation of the poly(alkylene oxide) compound (A) is effected byreacting the haloalkylcarboxylic acid of the general formula II orarylsulfonyl halides of the formula III with corresponding poly(alkyleneoxide) derivatives (such as, for example, monoalkyl ethers) by knownmethods, where the poly(alkylene oxide) compound (A) may be regarded asa macroinitiator.

If Z is a chain-transferring group, the poly(alkylene oxide) compound(A) may also be regarded as a macromolecular chain transfer agent whichis reacted with the monomer component (B) in a conventional free radicalpolymerization. In the case of this synthesis route, which can becarried out by the known methods, the building block Z is a group whichis capable of acting as a chain transfer agent in a free radicalpolymerization. Owing to their high chain transfer rate, thiol groupsare preferably used here. The synthesis of the correspondingfunctionalized poly (alkylene oxides) correspond to the general priorart.

For the preparation of the block copolymers used according to theinvention, the poly(alkylene oxide) compound (A) is reacted with atleast one ethylenically unsaturated monomer compound (B) which forms theblock B. In the case of the block copolymers used according to theinvention, the designation “block” means that it is a polymer buildingblock which has a chemical composition differing from that of block A,which is derived from the poly(alkylene oxide) compound (A). Block B maybe both a homopolymer which is composed only of one type of monomer anda copolymer consisting of a plurality of types of monomers. If aplurality of types of monomers are used, these can be polymerizedaccording to the prior art preferably by means of ATRP, either randomly,blockwise or blockwise with random intermediate zones. A gradientstructure along the polymer chain is also possible.

Furthermore, the ATRP also permits the synthesis of branched polymerchains. The block copolymers used according to the invention cantherefore have a linear or branched block B. The block copolymersaccording to the invention preferably have a linear block B which iscomposed of one type of monomer, a linear block B which consists of arandomly composed copolymer or a branched block B which consists of arandomly composed copolymer. Suitable monomers are ethylenicallyunsaturated compounds capable of undergoing (free radical)polymerization, in particular acrylates, methacrylates and styrenederivatives of the general formula (II)

R⁶ and R⁷ may be H, CH₃, COOH or salts thereof, COOR¹⁰ or CONR¹⁰R¹⁰,alkali metal (sodium, potassium), alkaline earth metal (calcium) orammonium salts preferably being used as carboxylic acid salts, and R¹⁰is H, C₁-C₁₂-alkyl, C₁-C₁₂-hydroxyalkyl,

and R¹, m and n have the abovementioned meaning. In formula II, R⁶ andR⁹ together may be —O—CO—O—, so that the corresponding monomers arederived from maleic anhydride. R⁶ may he H, CH₃ or CH₂—COOR¹⁰, R¹⁰having the abovementioned meaning. R⁹ may be COOR¹⁰, an optionallysubstituted C₆-C₁₄-aryl radical or OR¹¹, where R¹¹=acetyl or

and R¹, R¹⁰, m and n have the abovementioned meaning.

For the block copolymers prepared according to the invention, monomercompounds in which R⁶ and R⁷ are H or R⁶ and R⁹ together are O—CO—O, R⁸is H, CH₃ or CH₂—COOR¹⁰ and R⁹ is COOR10 or a phenyl radical optionallysubstituted by hydroxyl, carboxyl or sulfo groups are preferably used.Preferably, R⁶ and R⁷ are H, R⁸ is H or CH₃ and R⁹ is COOR¹⁰ and veryparticularly preferably R⁶ and R⁷ are H, R⁸ is H or CH₃, R⁹ is COOH orsalts thereof or COOR¹² and R¹² is tert-butyl or C₁-C₆-hydroxyalkyl.

Furthermore, according to a preferred embodiment, branches can beintroduced in a targeted manner into the block B of the block copolymersused according to the invention if, in addition to the monomer compounds(B), so-called inimers are also incorporated as polymerized units intothe block B. An inimer is understood as meaning a compound which hasboth a polymerizable ethylenically unsaturated double bond and a groupwhich can have an initiating effect in the context of ATRP. Particularlysuitable inimers are prepared by esterification ofhydroxy-functionalized monomers, such as, for example, hydroxyethylmethacrylate (HEMA) using ATRP initiators, such as 2-halopropionic acidsor 2-haloisobutyric acids.

Furthermore, it is also possible to use inimers prepared bysulfochlorination of styrene in the preparation according to theinvention.

The preparation of the block copolymers prepared according to theinvention is effected—as described above—by known methods, free radicalpolymerization and in particular ATRP being regarded as preferred.

According to a preferred embodiment, the reaction is effected in atemperature range of 20 to 110° C., depending on the solvent. In aproticsolvents or in the case of bulk polymerizations, in general temperaturesof from 50 to 110° C., preferably from 60 to 90° C., are used. In proticsolvents, in particular water, the polymerization begins under certaincircumstances at as low as 20° C.

The ratios of poly(alkylene oxide) compound (A) to monomer compound (B)can be varied within wide limits, but it has proven particularlyadvantageous to set this ratio of (A) to (B) to 1:5 to 1:300, inparticular 1:15 to 1:80.

As is known to the person skilled in the art in the area of ATRP,halides or oxides of transition metals of low oxidation state, which arecomplexed by (generally polydentate) ligands and brought (at leastpartly) into solution are used as catalysts. The most commonly used areCu(I) oxide, chloride or bromide, Fe(II) chloride or sulfate and Ni(II)chloride or bromide. Generally used ligands are 2,2′-bipyridine(optionally also substituted), pentamethyldiethylenetriamine (PMDETA),tris(2-dimethylaminoethyl)amine, triphenylphosphine or Schiff's bases of2-pyridinealdehyde and primary amines. For complexing of Cu—I salts, ingeneral two mole equivalents are used in the case of bidentate ligandsor one mole equivalent is used in the case of tridentate or tetradentateligands.

If the preparation of the block copolymers used according to theinvention is effected via free radical polymerization, it is possible torely on the customary azo or peroxo initiators.

The block copolymers proposed according to the invention areoutstandingly suitable as superplasticizers or dispersants for aqueoussuspensions of solids, the block copolymers preferably being used in anamount of from 0.01 to 5% by weight, based on the weight of thesuspension of solids. Here, the suspension of solids can containinorganic particles selected from the group consisting of crushed rock,silicate powder, chalk, clays, porcelain slip, talc, pigments and carbonblack or organic particles, such as, for example, plastics powders. Theuse of the block copolymers proposed according to the invention foraqueous binder suspensions based on cement, lime, gypsum and anhydriteis to be regarded as particularly preferred. There, the block copolymershave a substantially better water-reducing power at the same dose thanconventional superplasticizers based on comb copolymers. Moreover, whenthe block copolymers are used according to the invention, a reducedslump loss compared with conventional superplasticizers can also befound.

The examples which follow are intended to illustrate the invention inmore detail.

EXAMPLES

A) Preparation of poly(alkylene oxide) compound (A) (ATRPmacroinitiators) according to formula I

The preparation method used was the azeotropic esterification withcarboxylic acids.

For this purpose, a two-necked flask is equipped with stirrer, waterseparator and reflux condenser. The flask is filled with 0.1 mol of thecorresponding poly (alkylene oxide) monoalkyl ether and with 0.5 mol ofbromoisobutyric acid or bromopropionic acid, 0.005 mol ofp-toluenesulfonic acid and 50 ml of toluene. The reaction mixture isrefluxed while stirring until no more water is separated off.

Thereafter, 500 ml of methanol are added and refluxing is carried outwhile stirring until free carboxylic acid is no longer detectable in thereaction mixture by means of GC, HPLC or TLC. The excess methanol isremoved by distillation together with the resulting methyl ester ofbromoisobutyric acid or of bromopropionic acid. The distillation residueconsists of the desired ATRP macroinitiator. Further purification stepsare generally not necessary.

The following ATRP macroinitiators were synthesized according to thismethod:

Starting from polyethylene glycol monomethyl ethers having the averagemolecular weights

-   a) 500 g/mol of the corresponding bromoisobutyric esters (1)-   b) 1100 g/mol of the corresponding bromoisobutyric esters (2)-   c) 2000 g/mol of the corresponding bromopropionic esters (3)-   d) 5000 g/mol of the corresponding bromopropionic esters (4)    B) Preparation of different block copolymers according to the    invention by ATRP

“Atom transfer radical polymerization” was effected in a three-neckedflask which was equipped with a gas-tight stirrer, condenser, nitrogeninlet tube and vacuum connection. The monomer used was tert-butylmethacrylate, which had been rendered inhibitor-free beforehand byfiltration over a bed of basic alumina.

First, the respective macroinitiator (1 to 4) was melted and wasinitially introduced into the flask together withpentamethyldiethylenetriamine (PMDETA) as a complexing agent and thetert-butyl methacrylate (t-BMA). The apparatus and the reaction mixturewere then rendered oxygen-free by repeated application of a vacuum, ineach case followed by flooding with nitrogen. Thereafter, copper(I)chloride was added as a catalyst and freedom from oxygen was once againensured. The amounts of the starting materials are shown in table 1.

The reaction mixture was then heated to 90° C. for two hours whilestirring. After two hours, the highly viscous reaction mixture wascooled and traces of unconverted monomer were distilled off in vacuo.

The block copolymer according to the invention which was thus obtainedwas dissolved in dioxane, 5 g of sulfuric acid were added and refluxingwas effected for two hours with stirring. Cleavage of the tert-butylester groups occurs with elimination of gaseous isobutylene, andcarboxyl groups are formed. After the end of the gas evolution, thedioxane was removed by distillation. The block copolymer according tothe invention which was obtained was dissolved in three times the amountof water, the pH being adjusted to 8 by means of aqueous NaOH solution.The exact determination of the solids content of the solution waseffected by evaporating the water on a heatable balance at 130° C. toconstant weight.

The average molecular weights were determined by means of GPC. Themobile phase used was a mixture of 80% by volume of aqueous 5% strengthammonium formate solution and 20% by volume of acetonitrile. HEMAcolumns were used as stationary phases and the calibration in the caseof RI detection was effected by means of different polyethylene glycolstandards. Since the synthesized polymers are copolymers, the molecularweights determined via polyethylene glycol calibration may differslightly from the real values.

The stoichiometries of the respective polymerization batches and theaverage molecular weights and polydispersities determined by means ofGPC are shown in table 1.

TABLE 1 Linear block copolymers M_(w) M_(n)/ after M_(w) Macro- Macro-hydro- after initia- initiator t-BMA CuCl PMDETA Prod. lysis hydro- torNo. [mol] [g] [mol] [g] [mol] [g] [mol] [g] No. [g/mol] lysis 1 0.046 300.25 35 0.046 4.51 0.046 8.1 1-1 1260 1.18 1 0.031 20 0.46 65 0.031 3.040.031 5.5 1-2 2150 1.29 1 0.015 10 0.46 65 0.015 1.47 0.015 2.6 1-3 35801.33 2 0.032 40 0.32 45 0.032 3.14 0.033 5.6 2-1 2470 1.32 2 0.024 300.49 70 0.024 2.35 0.024 4.2 2-2 4360 1.18 2 0.016 20 0.63 90 0.016 1.570.016 2.7 2-3 5100 1.20 3 0.021 45 0.21 30 0.021 2.06 0.021 3.7 3-1 44901.36 3 0.011 24 0.42 60 0.011 1.08 0.011 1.9 3-2 6300 1.24 3 0.0056 120.42 60 0.006 0.55 0.006 1 3-3 9280 1.09 4 0.0106 55 0.32 45 0.011 1.040.011 1.9 4-1 9160 1.27 4 0.0053 27 0.28 40 0.005 0.52 0.005 0.9 4-210660 1.23 4 0.0053 27 0.42 60 0.005 0.52 0.005 0.9 4-3 13530 1.29

Furthermore, a block copolymer according to the invention and having abranched polymethacrylic acid block was also synthesized by using aninimer. The reaction was carried out as described above, except thathere, in addition to the macroinitiator (2), hydroxyethyl methacrylateisobromobutyric ester was added as an inimer. The further working-up waseffected as described above.

The stoichiometries of the respective polymerization batches and theaverage molecular weights and polydispersities determined by means ofGPC are shown in table 2.

TABLE 2 Block copolymers having a branched poly (methacrylic acid) blockM_(w) M_(n)/ after M_(w) Macro- Macro- hydro- after initia- initiatorInimer t-BMA CuCl PMDETA Prod. lysis hydro- tor No. [mmol] [g] [mmol][g] [mol] [g] [mmol] [g] [mmol] [g] No. [g/mol] lysis 2 5 6.34 5 1.40.35 50 10 1 10 1.7 2-4 20750 1.29 2 20 25 20 5.6 0.35 50 40 4 40 6.92-5 6000 1.27C) Cement paste tests for determining the water-reducing power

By mixing the abovementioned block copolymers according to the inventionwith cement paste, the water-reducing power was tested in comparisonwith the commercially available concrete additive Glenium®-27. TheGlenium®-27 is a random comb polymer of polymethacrylic acid withpolyethylene glycol side chains. The side chains have an averagemolecular weight of about 1100 g/mol.

For testing the water-reducing power, a cement of the type “Almendingen32.5 NW-HS” was mixed with water in the ratio w/c=0.32 and therespective concrete additive (Glenium®-27 or one of the block copolymersaccording to the invention which are described above) was added in adose of 0.2% by weight solid/cement (cf. table 3).

For determining the degree of mini-slump, a truncated cone(D/d/H=40/20/60 mm) is used. With the aid of a small attached funnel,the truncated cone is filled with the binder paste without a compactingeffect and the projecting paste is scraped off. After the cone has beenraised, the slump is determined.

The results of various cement paste slump tests are summarized in table3.

TABLE 3 Results of cement paste slump tests using Almendingen 32.5 NW-HSConcrete Dose, based additive on cement Slump designation [% by wt.] W/C[cm] None 0 0.32 too stiff Glenium ® -27 0.2 0.32 14.8 1-1 0.2 0.32  9.81-2 0.2 0.32 12.3 1-3 0.2 0.32 14.7 2-1 0.2 0.32 17.5 2-2 0.2 0.32 16.82-3 0.2 0.32 16.5 2-4 0.2 0.32 17.0 2-5 0.2 0.32 16.9 3-1 0.2 0.32 17.13-2 0.2 0.32 17.6 3-3 0.2 0.32 16.7 4-1 0.2 0.32 17.8 4-2 0.2 0.32 17.24-3 0.2 0.32 16.3

With the exception of the polymers based on (1) (polyethylene glycolmonomethyl ether having a molecular weight of 500 g/mol), all otherblock copolymers according to the invention have a consistently betterplasticizing effect in the cement paste than Glenium®-27.

D) Mortar tests for the determination of the water-reducing power andretention of the flowability over a period of 30 min

The test was carried out according to (DIN EN 1015-3).

The cement used was Schelklingen CEM II 42.5 R.

TABLE 4 Results of the mortar slump tests using CEM II 42.5 RSchelklingen Concrete Dose additive [% by w/c s/c Slump (cm) designationwt.] [kg/kg] [kg/kg] 4 min 30 min Glenium ®-27 0.2 0.47 2.7 24.2 24.32-1 0.2 0.45 2.7 24.0 22.9 2-2 0.2 0.45 2.7 25.2 24.3 2-3 0.2 0.45 2.724.7 24.0 1-2 0.2 0.45 2.7 22.8 21.8 2-4 0.2 0.45 2.7 26.7 24.4 2-5 0.20.45 2.7 27.8 25.7

The results clearly show that, even at a lower water content (w/c=0.45),the block copolymers used according to the invention generallyplasticize better than Glenium®-27 at w/c=0.47. The good plasticizingeffect is maintained virtually unchanged over a period of at least 30min.

1. A method of dispersing aqueous suspensions of solids, the methodcomprising: blending block copolymers with an aqueous suspension ofsolids, the suspension of solids including hydraulic binders whichinclude materials selected from the group consisting of cement, lime,gypsum, anhydrite and mixtures thereof, wherein the block copolymers areprepared by reacting a poly(alkylene oxide) compound of the generalformula (I)

in which R¹=hydrogen, a C₁—C₂₀-alkyl radical, a cycloaliphaticC₅—C₁₂-cycloalkyl radical, an optionally substituted C₆—C₁₄-arylradical; m=2 to 4; n=1 to 250; and Z is selected from the group offormulas III, IV, and V

where Y═O or NR² R²=H,a C₁—C₁₂-alkyl radical, a C₆—C₁₄-aryl radical, or

X=Cl or Br m′=1 to 4 n′=0 to 2,

where R³=an optionally substituted C₆—C₁₄-arylene radical X=Cl or Br,

in which R⁴ is H, a C₁—C₁₂ alkyl radical, a C₅—C₈-cycloalkyl radical, aC₆—C₁₄-aryl radical, optionally substituted by hydroxyl, carboxyl orsulfo groups, or

and R⁵ is C₁—C₁₂ alkyl, C₆—C₁₄-aryl, or

and R¹, R², m and n have the abovementioned meaning, with anethylenically unsaturated monomer compound of the general formula (II)in a free radical, anionic or cationic polymerization

in which R⁶ and R⁷ may be H, CH₃, COOH or salts thereof, COOR¹⁰CONR¹⁰ R⁶and R⁹ together may be O—CO—O R⁸ may be H, CH₃ or —CH₂—COOR¹⁰ R⁹ may beCOOR¹⁰, an optionally substituted C₆—C₁₄-aryl radical or OR¹¹ R¹⁰ may beH, C₁—C₁₂-alkyl, C₁—C₁₂-hydroxyalkyl, R¹¹ may be acetyl, and R¹, m and nhave the abovementioned meaning.
 2. The method as claimed in claim 1,wherein the reaction of the poly(alkylene oxide) compound with themonomer compound is carried out in the form of a free radicalpolymerization.
 3. The method as claimed in claim 2, wherein thereaction is effected in the form of an atom transfer radicalpolymerization.
 4. The method as claimed in claim 1, wherein the arylradicals for R¹ are also substituted by hydroxyl, carboxyl and sulfogroups.
 5. The method as claimed in claim 1, wherein in formula (I), mis 2 or 3 and n is 5 to
 250. 6. The method as claimed in claim 1,wherein R² is hydrogen or C₁—C₂-alkyl radical.
 7. The method as claimedin claim 1, wherein m′ is 1 and n′ is 0 or
 1. 8. The method as claimedin claim 1, wherein the arylene radical R³ also has halo, hydroxyl,C—C₁₂-alkoxy, C₁—C₁₂- dialkylamino or carboxyl groups.
 9. The method asclaimed in claim 1, wherein R⁶ and R⁷ are H,R⁶ and R⁹ together areO—CO—O, R⁸ is H,CH₃ or CH₂COOR¹⁰ and R⁹ is COOR¹⁰ or is a phenyl radicaloptionally substituted by hydroxyl, carboxyl or sulfo groups.
 10. Themethod as claimed in claim 9, wherein R⁶ and R⁷ are H, R⁸=H or CH₃ andR⁹=COOR¹⁰.
 11. The method as claimed in claim 10, wherein R⁶ and R⁷ areH,R⁸=H or CH₃ and R⁹ is COOH or salts thereof or COOR¹² where R¹² istert-butyl or C₁—C₆-hydroxyalkyl.
 12. The method as claimed in claim 1,wherein the reaction of the poly (alkylene oxide) compound and themonomer compound is carried out in the presence of a inimer compound.13. The method as claimed in claim 12, wherein the inimer compound isprepared by esterification of hydroxy-functionalized monomers with ATRPinitiators.
 14. The method as claimed in claim 12, wherein the inimercompound is prepared by sulfochlorination of styrene.
 15. The method asclaimed in claim 1, wherein the reaction is effected in the temperaturerange from 20 to 110° C.
 16. The method as claimed in claim 1, whereinthe block copolymers are used in an amount of 0.01 to 5% by weight,based on the suspension of solids.
 17. The method as claimed in claim16, wherein the suspension of solids further includes inorganicparticles selected from the group consisting of crushed rock, silicatepowder, chalk, clays, porcelain slip, talc, pigments and carbon black.18. The method as claimed in claim 16, wherein the suspension of solidscontains organic particles.
 19. A method of superplasticizing aqueoussuspensions of solids, the method comprising: blending block copolymerswith an aqueous suspension of solids to superplasticize the suspensionof solids, the suspension of solids including hydraulic binders whichinclude materials selected from the group consisting of cement, lime,gypsum, anhydrite and mixtures thereof, wherein the block copolymers areprepared by reacting a poly(alkylene oxide) compound of the generalformula (I)

in which R¹=hydrogen, a C₁—C₂₀-alkyl radical, a cycloaliphaticC₅—C₁₂-cycloalkyl radical, an optionally substituted C₆—C₁₄-arylradical; m=2 to 4; n=1 to 250; and Z is selected from the group offormulas III, IV, and V

where Y=0 or NR² R²=H, a C₁—C₁₂-alkyl radical, a C₆—C₁₄-aryl radical, or

X=Cl or Br m′=1 to 4 n′=0 to 2,

where R³=an optionally substituted C₆—C₁₄-arylene radical X=Cl or Br,

in which R⁴ is H, a C₁—C₁₂ alkyl radical, a C₅—C₈-cycloalkyl radical, aC₆—C₁₄-aryl radical, optionally substituted by hydroxyl, carboxyl orsulfo groups, or

and R⁵ is C₁—C₁₂ alkyl, C₆—C₁₄-aryl, or

and R¹, R²,m and n have the abovementioned meaning, with anethylenically unsaturated monomer compound of the general formula (II)in a free radical, anionic or cationic polymerization

in which R⁶ and R⁷ may be H, CH₃,COOH or salts thereof, COOR¹⁰,CONR¹⁰R¹⁰ R⁶ and R⁹ together may be O—CO—O R⁸ may be H, CH₃ or—CH₂—COOR¹⁰ R¹⁰ may be COOR¹⁰,an optionally substituted C₆—C₁₄-arylradical or OR¹¹ R¹⁰ may be H, C₁—C₁₂-alkyl, C₁—C₁₂-hydroxyalkyl, R¹¹ maybe acetyl, and R¹, m and n have the abovementioned meaning.
 20. Themethod as claimed in claim 19, wherein the reaction of the poly(alkyleneoxide) compound with the monomer compound is carried out in the form ofa free radical polymerization.
 21. The method as claimed in claim 20,wherein the reaction is effected in the form of an atom transfer radicalpolymerization.
 22. The method as claimed in claim 19, wherein the arylradicals for R¹ are also substituted by hydroxyl, carboxyl and sulfogroups.
 23. The method as claimed in claim 19, wherein in formula (I), mis 2 or 3 and n is 5 to
 250. 24. The method as claimed in claim 19,wherein that R² is hydrogen or C₁—C₂-alkyl radical.
 25. The method asclaimed in claim 19, wherein m′ is 1and n′ is 0 or
 1. 26. The method asclaimed in claim 19, wherein the arylene radical R³ also has halo,hydroxyl, C₁—C₁₂-alkoxy, C₁—C₁₂-dialkylamino or carboxyl groups.
 27. Themethod as claimed in claim 19, wherein R⁶ and R⁷ are H,R⁶ and R⁹together are O—CO—O, R⁸ is H, CH₃ or CH₂COOR¹⁰ and R⁹ is COOR¹⁰ or is aphenyl radical optionally substituted by hydroxyl, carboxyl or sulfogroups.
 28. The method as claimed in claim 27, wherein R⁶ and R⁷ areH,R⁸=H or CH₃ and R⁹=COOR¹⁰.
 29. The method as claimed in claim 28,wherein R⁶ and R⁷ are H,R⁸=H or CH₃ and R⁹ is COOH or salts thereof orCOOR¹²,where R¹² is tert-butyl or C₁—C₆-hydroxyalkyl.
 30. The method asclaimed in claim 19, wherein the reaction of the poly (alkylene oxide)compound and the monomer compound is carried out in the presence of ainimer compound.
 31. The method as claimed in claim 30, wherein theinimer compound is prepared by esterification of hydroxy-functionalizedmonomers with ATRP initiators.
 32. The method as claimed in claim 30,wherein the inimer compound is prepared by sulfochlorination of styrene.33. The method as claimed in claim 19, wherein the reaction is effectedin the temperature range from 20 to 110° C.
 34. The method as claimed inclaim 19, wherein the block copolymers are used in an amount of 0.01 to5% by weight, based on the suspension of solids.
 35. The method asclaimed in claim 34, wherein the suspension of solids further includesinorganic particles selected from the group consisting of crushed rock,silicate powder, chalk, clays, porcelain slip, talc, pigments and carbonblack.
 36. The method as claimed in claim 34, wherein the suspension ofsolids contains organic particles.